BRACHIAL PLEXUS OF NERVES IN MAN 309 



intermediate trunk before this divides into dorsal and ventral 

 branches (fig". 24). 



The caudal trimk 



The caudal trunk is formed by the union of the first thoracic 

 and the eighth cervical nerves in 166 of the 175 plexuses or in 

 95.42 per cent (fig. 1). It then divides into dorsal and ventral 

 divisions in 165 of them. In the other case the caudal trunk 

 divides into the ulnar and the medial head of the median nerve 

 and this gives off a dorsal branch. In 4 of the above 166 cases 

 the eighth cervical nerve before joining the first thoracic gives 

 off a small branch. This joins the lateral fasciculus of the 

 plexus in 2 (fig. 27), the lateral head of the median nerve in 1 

 (fig. 25) and the ventral division of the intermediate trunk in 1. 

 In 2 of the 166 the caudal trunk, before dividing into dorsal and 

 ventral branches, gives off a small ventral ramus that joins 

 the intermediate trunk in 1 (fig. 6), and the lateral fasciculus of 

 the plexus in the other (fig. 8). 



In 6 plexuses, the eighth cervical nerve divides into dorsal 

 and ventral branches. The ventral branch joins the first thora- 

 cic nerve to form the medial fasciculus. There is no dorsal branch 

 of the first thoracic (fig. 26). There is no caudal trunk that 

 divides into dorsal and ventral divisions. 



In 2 instances, both the eighth cervical and first thoracic nerves 

 divide into dorsal and ventral branches and the ventral branches 

 join to form the medial fasciculus. These and the proceeding 

 6 cases are perhaps produced by the dissector removing more than 

 the usual amount of the connective tissue sheath, and it is not im- 

 possible that nerve fibers may have been broken through although 

 no broken ends were found at the time the plexus was verified. 



In one plexus the eighth cervical and first thoracic nerves join 

 to form the caudal trunk which after receiving a branch from the 

 intermediate trunk divides into dorsal and ventral divisions. 



The lateral fasciculus of the plexus 



The lateral fasciculus of the plexus is formed by the junction 

 of the ventral divisions of the cephalic and intermediate trunks 



